Quantcast Sediment Grain Size

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4.
Previous dredged or fill discharges;
5.
Landfill leachate/groundwater discharges;
6.
Spills of oil or chemicals;
7.
Releases from Superfund and other hazardous waste sites;
8.
Illegal discharges;
9.
Air deposition;
10.
Biological production (detritus); and
11.
Mineral deposits.
Finally, conditions that could potentially cause contamination of the material prior to its
excavation are listed in the ITM (p. 4-4) as:
1.
Bathymetry;
2.
Water current patterns;
3.
Tributary flows;
4.
Watershed hydrology and land uses;
5.
Sediment and soil types; and
6.
Sediment deposition rates.
The USACE and the USEPA will likely require a confirmation process with the above-listed
items as a checklist to be reasonably certain that potential beach fill is chemically compatible
with receiving beaches. In the event that BEACON requires chemical testing of beach fill
material, a sampling/testing plan will be developed for that specific source consistent with
USACE guidelines and approved by the USACE and USEPA prior to the testing. Test results
will be interpreted by the resources agencies for a determination of material acceptability.
4.2.2
Sediment Grain Size
The objective of specifying an acceptable range of grain sizes for the beach fill is to define a
maximum fines content for the material based on replicating natural sedimentation processes
while remaining within agency constraints. The ITM (p. 2-5) notes that the major evaluation
effort must be placed on deposited material and its effect on the benthic environment. The ITM
(p. 3-6) emphasizes the "reference sediment" concept. Applied to the South Central Coast Beach
Enhancement Program, the reference sediment approach could be interpreted as follows:
1.
The total amount of fine-grained sediment (clays and silts, passing the #200 sieve or less
than 0.074 millimeters in diameter) introduced artificially into the littoral zone (portion of
fines times total volume of beach fill) should not exceed the quantity of fines at beaches
at the point of discharge. However, internal USACE guidelines (Russ Kaiser, USACE,
personal communication, 2000) indicates that the fines content may be up to 10% above
existing fines at the location of placement. Section 3.0 outlines each beach fill site and
4-6
Moffatt & Nichol Engineers



 


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